Process of making tetraphosphates



UNITED STATES PATENT OFFICE PROCESS OF MAKING TETRAPHOSPHATES AugustusH. Fiske, Warren, and Charles S. Bryan,

Providence, R; I., assignors to Rumiord Chemical Works, Rumford, R. I.

No Drawing. Application December 7, 1934, Serial No. 756,457

3 Claims.

Our invention relates particularly to a method of producingtetraphosphates and especially tetraphosphates of the alkali metals, andproduct thereof.

The object of our invention is to provide an advantageous, inexpensiveand expeditious meth- 0d, and product thereof, of producing suchtetraphosphates, and particularly the alkali metal tetraphosphates. Thetetraphosphates to which we refer are the salts of the tetraphosphoricacid discovered by Fleitmann and Henneberg in 1848 and having thefollowing constitution, as set forth by Roscoe and Schorlemmer in theirTreatise on Chemistry, vol. 1, Macmillan & Co., Ltd., 1905, page 656,-

Tetraphosphoric acid I ro-on PO-OH This is not to be confused with theso-called tetraphosphate fertilizer discovered by Stoppani in 1911, andwhich was made by heating the carbonates of sodium, magnesium, calciumand sulphate of sodium with natural mineral phosphates to a temperatureof about 600 C., a process developed to make the mineral phosphatemerely available as a plant food. The product made by Stoppani wasdoubtless called tetraphosphate because of the fact that fouringredicuts were used in its preparation, in addition to the mineralphosphate present, and the name applied thereto was evidently merely atrade term, his product being understood to be a double orthophosphateof calcium and sodium. The tetraphosphates produced by Fleitmann an'dHenneberg have the general formula R6P4013, where R signifies the base,and were made up then by fusing together pyrophosphates and ing thesubject matter of the present application, are the salts of the acidthere referred to.

While our invention is capable of being carried out in different ways,for the purpose of illustra tion we shall describe only certainprocedures in 5 connection with the same, by way of example.

We have discovered that when phosphoric pentoxide, P205, preferably inthe form of a powder, and sometimes known as phosphoric anhydride, ismixed with a base derived from one of the alkali metals, as, forinstance, sodium or potassium hydroxide, also preferably in a powdereddry state, a violent chemical reaction takes place accompanied by theevolution of heat, for example, in accordance with the followingequation:

The water being driven off by the heat evolved, there is left a drywhite homogeneous powder of uniform composition having valuableproperties 20 and uses. In accordance with the above reaction, forexample, there may be brought together for this purpose 10 parts byweight of phosphoric pentoxide and 8.5 parts by weight of sodiumhydrate. If, for example, potassium tetraphosphate is to be formed therewould be used, instead, 1 part by weight of phosphoric pentoxide and11.9 parts by weight of potassium hydroxide.

Furthermore, it has been found that monosodium metaphosphate, NaPOa, orsome of its polymeric forms, either alone or mixed with sodiumpyrophosphate, N84P20'1, is valuable as a solvent for calcium ormagnesium salts and has, accordingly, been used for the softening ofwater and other similar purposes. We have found, however, that thetetraphosphates are considerably more valuable and eifective than themetaphosphates and admixtures thereof, as the same or better results canbe obtained with the tetra- 40 phosphates such as are made in accordancewith our invention, by using only three fourths as much of thetetraphosphate by weight as compared with the amount of metaphosphate orother admixtures previously used. Undoubtedly the value of the saidtetraphosphates in this connection, for instance in the case of thetreatment of water containing dissolved calcium or magnesium compoundsor both, arises largely from decreasing the concentration of the calciumor 50 magnesium ion or both in solutions to which the tetraphosphatesare added, or, in other words, by causing the calcium and'magnesium ionpresent in the water to be brought into very slightly ionized solublechemical compounds with the 55 tetmphosphates. In other words, we havefound that the tetraphosphates made in accordance with our inventionhave properties of superior value in connection with the following uses,for example:

As a water softener by keeping the alkali earth bases in a solublecondition. 7

In laundries to save soap by combining with the alkali earth bases inthe washing water.

In deliming leather as in the tanning industry.

In dissolving the lime compounds which. may occur in soiled textiles.

To prevent deposits of alkali earth salts forming in hot water systems.

To prevent deposits of alkali earth compounds in steam boilers and theirfeed lines.

To prevent deposits of alkali earth compounds in automobile watercooling systems.

To prevent the formation of alkali earth bases as precipitates in thewater to be frozen in artificial ice machines.

To prevent the formation of alkali earth precipitates on the outside ofcans from the cooling water of the canning industry.

To prevent streaky dyeing in textiles by keeping any alkali earthcompounds in a condition of solubility.

Preventing the formation of soap spots on the cloth in dyeing.

To clean cement or brick walls from lime deposits.

As a softener for water in washing living animals or in baths for humanbeings.

For cleaning or washing dishes.

For softening water in which anything may be washed and thus savingsoap.

Washing rayon, for instance.

Scouring wool.

Kier boiling in bleacheries.

Boiling off silk.

Causing increased penetration of dye in textiles by cleaning off tracesof alkali earth compounds.

While we have described our invention above in detail we wish it to beunderstood that many changes may be made therein without departing fromthe spirit of the same.

We claim:

1. A process which comprises producing a tetraphosphate by reactingphosphoric pentoxide with an alkali metal hydroxide in substantiallytheir theoretical proportions, to make a tetraphosphate.

2. A process which comprises producing a tetraphosphate by reactingphosphoric pentoxide with sodium hydroxide in substantially theirtheoretical proportions, to a make a tetraphosphate.

3. A process which comprises producing a tetraphosphate by reactingphosphoric pentoxide with potassium hydroxide in substantially theirtheoretical proportions, to make a tetraphosphate.

AUGUSTUS H. FISKE. CHARLES S. BRYAN.

